A comparison of the concentrations of heavy metals in modern and medieval shells of swollen river mussels (Unio tumidus) from the Szczecin Lagoon, SW Baltic basin

The shells of mussels, live-collected bivalves or during archaeological excavations, can be used as bioindicators of current and historical levels of heavy metal contamination. In this study, we examined the shells of Unio tumidus, commonly found in the Baltic Sea region, and determined the concentrations of Zn, Cu, Fe, Pb, Ni, and Cd in samples from the 10th, 11th, and 21st century from the area of the Szczecin Lagoon. The average levels of heavy metals (in mu g g(-1) dry weight) in the shells from the Middle Ages were: 137.5 (Fe), 3.87 (Zn), 0.789 (Cu), 0.012 (Pb), 0.047 (Ni), and 0.0009 (Cd). Shells from the 21st century were significantly (P<0.05) more abundant in Fe, Cu, Ni, Pb, and Cd (rates of increase: 1.96x, 3.54x, 2.71x, 2.08x, and 3.55x, respectively) than shells from the Middle Ages. These results reflect contemporary anthropogenic pollution of the environment with heavy metals and confirm the possibility of using U. tumidus shells in the assessment of heavy metal pollution levels.

Automated summary

The study examined shellfish shells as bioindicators of heavy metal pollution levels over different centuries, showing a significant increase in heavy metal content in shells from the 21st century compared to those from the Middle Ages, reflecting contemporary anthropogenic pollution.